• Chul Ho Chang, Seung Ho Choi, Yon Hee Shim, Ki-Young Lee, Hwan-Mo Lee, and Yang-Sik Shin.
• Department of Anesthesiology and Pain Medicine, and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, CPO Box 1217, Seoul 120-752, Republic of Korea.
• Spine. 2006 Oct 1;31(21):E813-6.

Study DesignA prospective randomized study on the end-tidal concentrations of sevoflurane at which ankle clonus existed.Summary Of Background DataThe ankle clonus reflex is a transient neurologic abnormality, which normally occurs in patients during emergence from general anesthesia.ObjectiveTo determine the optimal end-tidal concentration of sevoflurane to test an ankle clonus in children during emergence from general anesthesia.MethodsWe studied 30 children (aged 5-15 years). General anesthesia was induced with thiopental sodium. Anesthesia was maintained with sevoflurane, oxygen, and air. At completion of surgery, 3% volume of the end-tidal sevoflurane concentration was maintained for at least 10 minutes. Ankle clonus was checked at 1.0% to 0.1% volume of the end-tidal sevoflurane concentration with an interval of 0.05% volume.ResultsOf children, 80% had bilateral ankle clonus, which was found most frequently when patients responded poorly to verbal commands. The median of the end-tidal sevoflurane concentration for a reactive ankle clonus was 0.45% volume (interquartile range 0.5% to 0.4% volume).ConclusionsThe ankle clonus should be tested at 0.45% volume of end-tidal sevoflurane concentration in children undergoing scoliosis surgery during emergence from the general anesthesia.

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